But researchers see no reason for parental alarm

(CNN) -- Young children in day care are slightly less likely to bond well with their mothers than stay-at-home children, according to newly released information from an ongoing federal study. But researchers, hoping parents won't be alarmed unnecessarily, caution the results are preliminary and say there's no way to judge how much time in day care may be too much.

The findings from the government's National Institute of Child Health and Human Development (NICHD) Study of Early Child Care are in the November issue of Developmental Psychology, published by the American Psychological Association.

Researchers began tracking nearly 1,300 young subjects and their mothers in 1991 when the infants were 6 months old. Although they're now in third grade, the newly released portion of the study only covers the period from ages 6 months to 3 years.

It found a "small but significant" link between time spent in day care and how positively a child interacts with his/her mother.

Owens says working mothers should not quit their jobs over the study findings

"The more hours a child spends in child care, the slightly less positive mother-child interaction is," said Margaret Tresch Owen, a psychologist at the University of Texas at Dallas who helped collect the data.

But she conceded that researchers can't tell parents at what point the bonding begins to deteriorate.

"We don't have that finding and I wish we did," Owen told CNN. "I wish we could say, 'Here's the answer folks, 40 hours is fine and 50 hours is not fine.'"

This latest day care report contradicts more positive information about day care in years past. And with three out of five U.S. preschoolers already in some form of child care, the findings may reinforce the concerns of millions of parents worried that having their children in day care may not be a wise decision.

But researchers emphasize they see no cause for alarm or any lasting impact on overall child development. In short, working mothers don't need to quit their jobs, Owen said.

The study findings may reinforce some concerns parents have about putting their kids in day care

Child care providers say parents should be more concerned about the quality of care than the quantity of time a child spends away from home.

"I think you could probably get a study to say just about anything you wanted it too," said Cheryl Smith, director of the Downtown Child Development Center, a daycare facility in Atlanta.

"I think the bonding between mother and child does not have to be interrupted because of the child care arrangements that you choose," she told CNN.

The NICHD study will continue to follow the same test subjects until next year, when they reach fourth grade.